With the advent of digital communications technology, many TV program streams are transmitted in digital formats. For example, Digital Satellite System (DSS), Digital Broadcast Services (DBS), and Advanced Television Standards Committee (ATSC) program streams are digitally formatted pursuant to the well known Moving Pictures Experts Group 2 (MPEG-2) standard. The MPEG-2 standard specifies, among other things, the methodologies for video and audio data compression allowing for multiple programs, with different video and audio feeds, to be multiplexed in a transport stream traversing a single transmission channel. A digital TV receiver may be used to decode an MPEG-2 encoded transport stream, and extract the desired program therefrom.
In accordance with the MPEG-2 standard, video data may be compressed based on a sequence of groups of pictures (GOPs), made up of three types of picture frames, namely, intra-coded picture frames (“I-frames”), forward predictive frames (“P-frames”), and bilinear frames (“B-frames”). Each GOP may, for example, begin with an I-frame which is obtained by spatially compressing a complete picture using discrete cosine transformation (DCT). As a result, if a transmission error or a channel switch occurs, it is possible to resume correct decoding at the next I-frame. The GOP may represent additional frames by providing a much smaller block of digital data that indicates how small portions of the I-frame, referred to as macroblocks, move over time.
An I-frame is typically followed by multiple P- and B-frames in a GOP. Thus, for example, a P-frame occurs more frequently than an I-frame by a ratio of about 3 to 1. A P-frame is forward predictive and is encoded from the I- or P-frame that precedes it. A P-frame contains the difference between a current frame and the previous I- or P-frame. A B-frame compares both the preceding and the subsequent I- or P-frame data. The B-frame contains the average of matching macroblocks or motion vectors. Because a B-frame is encoded based upon both preceding and subsequent frame data, it effectively stores motion information.
Thus, MPEG-2 achieves its compression by assuming that only small portions of an image change over time, allowing the representation of these additional frames to be quite compact. Although GOPs have no relationship between themselves, the frames within a GOP have a specific relationship which builds off the initial I-frame.
The compressed video and audio data are typically carried by continuous elementary streams, respectively, which are broken into access units or packets, resulting in packetized elementary streams (PESs). These packets are identified by headers that contain time stamps for synchronizing, and are used to form MPEG-2 transport streams. For digital broadcasting, multiple programs and their associated PESs are multiplexed into a single transport stream. A transport stream has PES packets further subdivided into short fixed-size data packets, in which multiple programs encoded with different clocks can be carried. A transport stream not only includes a multiplex of audio and video PESs, but also other data such as MPEG-2 program specific information (sometimes referred to as metadata) describing the transport stream. The MPEG-2 metadata may include a program associated table (PAT) that lists every program in the transport stream. Each entry in the PAT points to an individual program map table (PMT) that lists the elementary streams making up each program. Some programs are open, but some programs may be subject to conditional access (encryption), and this information (i.e., whether open or subject to conditional access) is also carried in the MPEG-2 transport stream, typically as metadata.
The aforementioned fixed-size data packets in a transport stream each carry a packet identifier (PID) code. Packets in the same elementary streams all have the same PID, so that a decoder can select the elementary stream(s) it needs and reject the remainder. Packet-continuity counters may be implemented to ensure that every packet that is needed to decode a stream is received.
Video on demand (VOD) systems allow users to select and watch video content over a network. Some VOD systems “stream” content for real-time viewing. Others “download” the content to a set-top box before viewing starts. Use of digital video recorders (DVRs), also known as personal video recorders (PVRs), such as the TiVo® device (registered mark of TiVo Brands LLC, Alviso, Calif.) and the R Replay TV® device (registered mark of Digital Networks North America Inc., Pine Brook, N.J.), is ubiquitous. Such devices may provide some benefits to TV viewers. For example, a prior art DVR allows a user to record his or her favorite TV programs for later review, and to exercise a season-pass-like option wherein every episode of his or her favorite program is recorded for some period. Such devices may automatically record programs for the user based on his or her viewing habits and preferences. The presentation of the recorded programming content can be manipulated by exercising rewind, pause, skip and/or fast-forward functions (hereinafter referred to as “trick mode” or “trick play” functions) furnished by the DVR.
A “network PVR (NPVR)” (also referred to as an NDVR (Network Digital Video Recorder)) service allows the user to perform the analogous DVR functions through use of a network, rather than via a local DVR at the user premises. Unlike a DVR device, the NPVR service allows a user to “reserve” past and future programs for his or her review, even if such reserved programs were not identified by the user before their broadcast. Note that an NDVR can be distinguished from a DVR in that the latter, storage of programs and the like is local to the DVR, while in the former (NDVR) case, such storage is at the server or head end level.
United States Patent Application Publication Number 2006-0053456 of Brian E. Kelly, the complete disclosure of which is expressly incorporated herein by reference in its entirety for all purposes, discloses a technique for delivering, through a communications network, content of entertainment programs, and video recordings provided by users. In particular, a user may utilize a “home video on demand (HVOD)” service to distribute a video recorded using, e.g., a conventional camcorder, to desired viewers who have access to a broadband communications network, e.g., a cable TV network. The inventive system providing the HVOD service may receive from the user the video recording via email, postal mail, the Internet, computer transfer, etc. The inventive system converts the received video recording from its original video format to a uniform format. e.g., an MPEG-2 format. The converted video recording is stored in storage and made available to authorized viewers through the cable TV network.
United States Patent Application Publication Number 2004-0117837 of Jeyhan Karaoguz discloses a system and methods for communicating activity information to support user interaction during media broadcasts in a media exchange network. In an embodiment, a first user may associate a second user with particular media characteristics. Media characteristics may comprise, for example, subject and title keywords, a media channel type, a mode, a genre, an artist, a time period, and a language. The second user may be notified when the first user consumes media having pre-defined characteristics matching those associated with the second user. The second user may keep records of the consumption of media with particular media characteristics, and may provide services or incentives to the first user. A system may comprise a first and a second set top box, each having storage with an associated network address. A user of the second set top box may have at least one associated media characteristic, and the second user may be sent a notification when the first user requests media with pre-defined characteristics matching the media characteristic associated with the second user.
United States Patent Application Publication Number 2006-0026655 of Milton D. Perez discloses a system and method for managing, converting and displaying video content on a video-on-demand platform, including ads used for drill-down navigation and consumer-generated classified ads. A video-on-demand (VOD) content delivery system has a VOD Application Server which manages a database of templates ordered in a hierarchy for presentation of video content elements of different selected types categorized in hierarchical order. The templates include those for higher-order displays which have one or more links to lower-order displays of specific content. The VOD Application Server, in response to viewer request, displays a high-order templatized display, and in response to viewer selection of a link, displays the lower-order display of specific content. The hierarchical templatized displays enable viewers to navigate to an end subject of interest while having a unique visual experience of moving through a series of displays to the end subject of interest. For example, the higher-order display may be a product ad and the lower-order display may be an ad for a local retailer of the product. Similarly, a viewer can navigate from national product to local product ad, or classified ad category to specific classified ad, or bulletin board topic category to specific posting. In another embodiment, the VOD content delivery system is used to deliver consumer-generated classified ads on TV. A web-based Content Management System receives consumer-generated content uploaded online in industry-standard file formats with metadata for title and topical area, and automatically converts it into video data format compatible with the VOD content delivery system indexed by title and topical area. A User Interface for the system delivers listings data to the viewer's TV indexed by title and topical area, and displays a requested classified ad in response to viewer selection.
Outside the television field, there are certain photo-sharing techniques which allow people to upload photos via a web site and create their own shared folders, such that other people may view the shared photos over the Internet. There are also some software packages that convert photos and stream them over a video content network like a VOD file (that is, a video stream of a non-changing still image is transported, with all the associated bandwidth requirements). Where it is desired to view an album of photos, this type of software forms a single video from the album of photos, and adding new photos requires regenerating the entire video.